Have sleeved cylinders on my U 70". My problem has been with the material of the sleeves.

After one seasons with a tired bike I decided to go for "high compression" heads and when the old cast iron heads removed I noticed bad lines in the sleeves.I bored the sleeves from standard to .020" and mounted NOS rings in after market pistons.(...with alloy heads and fresh cylinders the bike was a rocket...)

The "standard" bore pistons were also aftermarket with thin hardened aftermarket rings....the sleeves looked like when you are really overheating the rings (glowing rings).But this had not been the case.

My theory is that my sleeves are in some hardened steel that must be used with some old type of non hardened rings.The situation is today OK but if I have had a chanse to drive with 0.050-0.060 bore without sleeves this would have been much better according to my knowledge both from a cooling perspective and from a material perspective.

My bike has runed 5000Km (3100 Miles) during 2007 and the cross marks after the grinding stones are almost gone..

My bike is now running very happily! Because of the possible trubles when you sleeve, I choosed to bore the front cylinder to +040. The bore senter was shiftes to the side where the deepest damage where. It did not clean up totaly, a very small "hole" is remaining with diameter less than the height of the piston ring. I'm going to take of the cylinder head after a few miles to inspect. So far so good. The rare cylinder remained +020 as this bore was OK!